The objectives of the research proposed herein are to determine the efficiency with which the central auditory system can separate out and attend to competing auditory messages. These objectives are important since the masking of speech by speech is a phenomenon which depends upon and invokes the functioning of very critical information processing mechanisms within the central nervous system. In the proposed experiments, listeners will be required to respond to a speech target presented (1) against a competing speech babble and (2) against a speech multiplied noise having the same temperal features and long term spectral characteristics of the speech babble. Both adults and children will be utilized as subjects. It is hypothesized that the speech target will require more intensity to be perceived when it is presented in the presence of the speech competition compared to when it is presented in the presence of the noise background. Moreover, this additional intensity required for the speech targent against the speech competition will be greater for children than for adults. Such a finding would demonstrate that children have more difficulty in teasing out a target speaker from a babble of other voices. These findings have important implications for basic theories of speech perception and the psychological concept of selective attention. Moverover, these findings would lay the groundwork for future studies involving the masking of speech by speech in language delayed children and children from culturally disadvantaged backgrounds.